Temperature control apparatus



June 17, 1930. L. A. M. PHELAN ET AL TEMPERATURE CONTROL APPARATUS FiledJan. 29. 1923 2 Sheets-Sheet 1 Toon Fraermsmr/c O d/7t June 17, 1930.PHELAN El AL TEQIPERATURE CONTROL APPARATUS Flled Jan 29 1923 2Sheets-Sheet 2 Patented June 17, 1930 UNITED STATES PATENT OFFICE LOUISA. M. PHELAN CLIFFORD H'OTCHKISS, 0F BELOIT, WISCONSIN, ASSIGNORS,

BY MESNE ASSIGNMENTS, TO INDIANA TIME-O-STAT CONTROLS COMPANY, OF ELK-HART, INDIANA, A CORPORATION OF MARYLAND TEMPERATURE CONTROL APPARATUSApplication filed January 29, 1923.

10 liquid fuel by means of a nozzle and a conduit connected to asuitable source of supply which is maintained under pressure by a pump,preferably an electric motor-operated pump.

One object of this invention is to provide a system'for automaticallyregulating and controlling the operation of an electric motor operatedpump'when used in connection with the above indicated type of oilburning apparatus.

In former attempts to provide a regulating system of the abQVecharacter, it has been the usual practice to make use. ofelectro-magnetic or motor operated relays. The use of such relays isundesirablerin many cases because of their complicated structure, andbecause of the widely varying frictional losses occurring at theirvarious mechanical bear-' ings. Such types of relays moreover areusually fitted with oommutators or contacting parts which are exposed tothe atmosphere and are consequently very unreliable in operation sincethese contacting parts very readily become oxidized and contaminated.

, A more particular object of this invention therefore is to provide anautomatic system for regulating combustion which eliminates the use ofmagnetic and motor operated relays and which also eliminates the use ofall exposed contacts.

A further object of this invention is to provide a reliable thermalrelay capable of use in the above indicated type of control system.

5 In certain types of oil burning systems as constructed at the presenttime, no provision is made for stopping the flow of the fluid fuel incase the intended ignition and com bustion for any reason do not takeplace in the fire box. Consequently, it is possible for poses.

Serial No. 615,530.

a great excess ofcombustible material to accumulate in the fire-boxunless the system is very carefully and constantly attended.

This may at times result in a serious fire hazard, as for instance, incase agas pilot flame is used in the furnace for ignition pur- If thepilot flame for any reason is accidentally extinguished and later theoil pump is started in operation, the "fire box will become flooded withfuel.

Hence, another particular object of this invention is the provision of adevice capable of use in the above indicated type of control system forpositively stopping the operation of the fuel pump when ignition andcombustion of the fuel does not actually take place.

A further object of our invention is to provide a system and apparatusof the above described character, which are comparatively simple inconstruction andeasy to install and which do not readily get out oforder.

Further objects and advantages of the invention will appear uponreference to the following specification and appended claims, takentogether With the drawings, in which Figure 1 is a diagrammatic view ofthe system comprising the invention asused in connection with a heatingfurnace and .also showing in a perspective view certain devices used inconnection with the system;

Fig. 2 is a diagrammatic view showing a portion of the system in amanner similar to the showing in Fig. 1, but showing the systemconnected without the use of a transformer;

Fig. 3 is a longitudinal sectional view of a thermostatic switch used atthe furnace fire box in the system shown in Fig. 1;

Fig. 4: is an end view with the cover removed of the device shown inFig. 3; i

Fig. 5 is an elevation view of the thermostatic relay device, which isshown in perspective in Fig. 1; and,

.Fig. 6 is an end view of the device shown in Fig. 5. 1

The system as shown in Fig. 1, and its operation, will first be outlinedin a general way before proceeding with a more detailed description ofits parts and operation.

Some of the elements of the system as used in connection with thecontrol of the combus- (power -D-, such for example, as the or inary 110volt lighting mains which are initially connected to the primary windingof a stepdown transformer E through a switch From the secondary windingof the transformer E, power is furnished to a circuit including awinding on a thermostatic relay element G and a room thermostatic switchH-. Providing the room thermostatic switch -H is closed, the currentthrough this circuit will at first cause heating in the thermostaticrelay element G which will in a short time serve to rotate the switch -Finto an open circuit position and also at the same time serve to rotatea switch I into a closed circuit position. The switch -I will then serveto connect the motor of the pumping equipment B- directly in series withthe power supply at D and thus the pump will be put into operation. I

The switch -F now bein in open circuit position, current through t eprimary 'of the transformer E must be supplied through another circuitif the thermostatic relay element G is to remain heated sufficiently tohold the switch I- in its closed circuit position, as required for thecontlnued operation of the fuel pump. In order to serve this purpose andalso to provide a safety device, another thermostatic switch J- ismounted at the combustion chamber 'A and is arranged to maintain aclosed circuit condition only whilecombustion is actually \taking placewithin the combustion chamher A. It will be seen from the diagram inFig. 1 that the initial circuit connection through the switch F- is thuslater replaced by a connection through the switches -J and -I- but,iffor any reason the fuel within the combustion chamber A does notignite, this circuit will remain open and the thermostatic relay elementG will not continue tobe heated. As a consequence, the switches F andI-- will be gradually turned back to their initial positions, asillustrated in Fig- 1, when the thermostatic relay element G becomescooled. This action will result in The various devices which areincluded in the1 system will now be described more in de-* tai Thethermal relay as used with this system is shown in detail in Figs. 5 and6 and by a schematic perspective view in Fi 1 and comprises a spirallywound bi-metal ic ribbon 10 which is fixed at one end to a support suchas at 11 by screws 12. The spiral ribbon 10 may.

be composed of superimposed strips of any two different metals orelements, referably brass and iron'which are selected ecause'. of theirwidely different coefiicients of expansion. When the temperature of thespiral ribbon 10 is altered, its shape will also be altered due to thedifferent coeflicients of expansion of the metals of which 'it. is made.To the other end of the spiral ribbon 10 a stub shaft 13 is fixed in anysuitable manner as by soldering. Upon the stub shaft 13, one or moreswitches as indicated at-F and Imay be mounted. In Fig. 1 the stub shaft13 is shown in extended and broken form for clearness of illustration.

The spiral ribbon 10 before bein wound into the spiral shape illustratedis rst covered with an insulating fabric 14, such for example asasbestos cloth saturated with any desirable insulating heat resistinadhesive, such as thick linseed oil. After being covered with thisinsulating fabric, the ribbon 10 is then provided with a resistancewinding 15 through which an electrical current may 7 be passed forcausing heating and consequent deformation ofthe spiral ribbon. .Thedimensions of the resistance winding 15 may be designed to accommodatethe particular current which is used and also to give the desired speedof operation or sensitiveness to.

the device. If a resistance winding producing a small heating effect isused, an appre'ci- 'a pair of fixed electrodes 16 and 17, which may beof substantial dimensions capable of carrying the full current used foroperating the motor of the pumping equipment above described. This motorcircuit may be termed that maincircuit while the circuit in which theresistance'winding I5 is included may be termed a control circuit. ThisswitchI-as shown is also provided with a third fixed electrode 18 ofsomewhat lighter constructionthan the electrodes 16 and 17 and'whic'h isused at certain times for the purpose of conducting currentto theresistance winding 15 of the thermostatic relay elementG- in the abovedescribed system. Thus the switch I- is common to. two circuits. Theelec trodes 16, 17 and 18, as shown, are fixed in the walls of a;container 19, preferablyformed of..g1ass and containing a body ofmercury which may come into-bridging relation with all three .of theelectrodes 16, 17 and18, when the container 19 is tilted the properamount. As shown 1n F 1g. 6, the container 19 is tilted to an angle suchthat the body of mercury 20 is in bridglng relation with all oftheelectrodes while in Fig. 1 the mercury is in bridging relation with noneof the electrodes. The container 19 is' preferably surrounded withprotecting means, such as a rubber band 21, wh1ch 1n turn is embracedbya spring clip 22 mounted upon the stub shaft 13.

The switch -F-- as used in the above described system. is also for thepurpose of making and breaking the current supplied to the circuitthrough the resistance coil 15 at certain times and is provided with apair of electrodes 23 and 24, which are adapted to be bridged by a bodyof mercury 25, as is I best shown in Fig. 1. The electrodes 23 and '24are'also fixedin the walls ofa container26,

preferably formed of glass and mounted upon the stub shaft 13' in amanner similar to the mounting of the container of the switch As will bereadily understood when the current ispassed-through the resistancewinding 15,, the spiral ribbon 10, because of the heat generated, willbecome altered 1n shape in a manner such that the shaft 13 and theswitches F and 'I will be rotated through a small angle about theiraxes. It will be noted that the switches F and 'I are attached tothestub shaft 13 at an angle such that the switch F-- will be in its closedcircuit position at times when the switch I isin its open circuitposition and conversely that when the switch --I is turned 'to itsclosed circuit position, the switch F- will be in its open circuitposition.

It will be also noted in Fig. 1 that the container26 of the switch F.-is formed in a slightly arched or curved shape so that the containermust be tilted a considerable amount beyond the horizontal before thebody of mercury 25 will roll to the opposite end of the container. Thisconstruction permits the actuation of the switch F- at a predeterminedtime interval after theactuation of the switch I and for particularreasons to be stated hereinafter.

The thermostatic switch J shown in Figs. 3 and 4, and which is mountedat the combustion chamber A--' will now be described in detail. -Ahousing 27 isprovided with a hollow bushing 28 for insertionin asuitable opening formed in a furnace door or other suitable portion ofthe furnace firebox. lVithin the. housing 27 an electric contactor 29 isPI'OVidQdyWhiCh is similar in construction to the contactor switch -I-described above,-'but is provided with only two electrodes 30 and 31,which correspond in position respectively to the electrodes 16 and 17 Abody of mercury 32 is adapted to roll into contact with the electrodes30 and 31 to complete a c rcuit therethrough when the con:

tactor is tilted sufficiently in the proper direc tion. The contactormay be surrounded with a protecting means 33, preferably formed of asestos twine in this instance, in order to resist the prevailingtemperatures occurring in the neighborhood of the fire box A. Theprotective means 33 is firmly embraced by a spring clip 34, which isfixed to a shaft '35,

which in turn is mounted in bearing 36 fixed 1n the housing 27. From thebearing 36 the shaft 35 extends out of thehousing coaxially through thehollow bushing 28 and also through an elongated tubular support or ex--tension 37 of the hollow bushing 28, and into the fire box -A-. It willbe noted that the bore of the tubular support 37 is of a diame- 'tersuch that theshaft 35 will always be in a widely spaced relation withthe walls of the support 37, thus eliminating frictional resistance tothe free movement of the shaft even if the parts should become seriouslywarped in the heated furnace. thermostatic bi-metallic element 38 has afixed end 39 attached to the end of the tubular sup- A spiral I port 37anda relatively free end 40 attached to the shaft 35 through a-hub 41.These ends of the spiral element 38 may be removably at.- tached by anysuitable means, such as by screws 42, as shown..

As will be readily understood, when the spiral element 38 is mountedwithin a fire box,

any substantial increase in temperature caused by combustion within thefire boxv will result in an alteration of the shape of the spiralelement, such as will cause the shaft 30 and 31 and thus maintain acircuit in closed condition. It will be noted that the spiral element38-is shown wound in a conical shape. This particular shape has severaldistinct advantages over the more common flat spiral form when used withthis construction, as for example, the various turns of the spiral areexposed to a greater extent to the air currents surrounding the deviceand hence are more quickly affected by any change in temperature. Thisparticular conical shape also permits the fixing of the end 39 to thetubular extension 37 in a rigid manner and at the same time permits theend 40 to be fixed to ment 38 is cold and no combustion is taking placeand so that it will be in closed circuit position when the combustionchamber be comes heated after ignition takes place. The container 29 maybe adjusted at this desired angular position by merely turning thebushing 28 with the entire housing 27 until the body of mercury 32 justrolls to the open circuit position upon the occurrence of thepredetermined desired drop in temperature within the combustion chamber.

The room thermostatic switch H- may be of any desired suitable type,such for example as is shown and described in the co- .pendingapplicationof Louis A. M. Phelan and Cliflord Hotchkiss, Serial No.544,589, filed March 17, 1922. This switch serves to open an electricalcircuit when the temperature of the room orcompartinent in which i it islocated rises to'a desired predetermined value and also serves to closethe circuit again after a predetermined drop in the temperature occurs.

In certain instances it may be cheaper and more convenient to installwiring to the room thermostatic switch which is particularly dethe motorcircuit.

signed for a lower voltage than is used .for

The transformer E- shown in Fig. 1 makes possiblethe use of lowervoltage in the circuit of the room thermostatic switch, if desired.However, the use of the transformer E- is. not essential to theoperation of the system and may be dispensed with by using theconnections shown in Fig. 2, where all of the circuits make use i. ofpower at the same voltage.

\ The complete operation of this system will now be described byoutlining the successive action of each of the devices upon placing thesystem in operation.

Assuming that the system has been put into proper order. as shown inFig. 1 and that the gas pilot C- has been lighted, it is merelynecessary for the operator to push a snap switch 43 in order to havecombustion take place in the fire box -A. From the switch 43 current islead through the switch F--, now closed, and through the primarywindingof the step-down transformer E-. From the secondary winding ofthe transformer -E, current will be led through the room thermostaticswitch-H (now assumed to be closed since the room to be heated is cold)and also through the resistance winding 15 upon the thermostatic element--G. The current through the resistance 15 will cause a heating of thespiral element 10 and the resulting change in shape of this element willserve to gradually turn the switches I and F. As the switch I- justpasses,

its horizontal position, the body of mercury 20 will roll into bridgingrelation with the three electrodes 16, 17 and 18. The bridging of theelectrodes 16 and 17 will place a pump motor 44 in series with powerfrom the switch 43. In the meantime the switch F will also be turned andthe body of mercury 25 will roll out of bridging relation with theelectrodes 23 and 24 into the open circuit position. The motor 44 nowbeing in operation, a spray of fuel will be supplied by a fuel pump 45from a tank 46 to the fire box A and in the ordinary course this spraywould be ignited by the pilot flame C. The heat of the burning spray offuel will serve to. actuate the thermostatic switch J and permit it toturn into a closed circuit position, as above described. The circuit tothe primary of the transformer -E- a through the switch --F havingalready become interrupted because of the turning of the switch F- willnow be resumed through the thermostatic switch J- in connection with theswitch -I--, the circuit through the switch I- following through theelectrode 18, the body of mercury 20 and the electrode 16 to the switch43.

As above described, the container 26 of the switch F is made in a curvedform so that the body of mercury 25 rolls to the open circuit positiononly when a definite time interval has elapsed after the actuation ofthe switch I. This time interval is sufiicient to permit thethermostatic element G to remain heated until after combustion takesplace and the fire box A- has become sufficiently heated to actuate thethermostatic switch -J. After the actuation of the thermostatic switchJ, the switch F-- is turned sufliciently to open the circuittherethrough and without any prolonged interruption of the flow ofcurrent through the resistance winding 15.

When the room in which the thermostatic switch H- is placed becomesheated to the desired temperature, the switch H will open the circuit,through the resistance winding 15 and consequently permit thethermostatic element G- to become cooled. As the thermostatic element G-becomes cooled, current to the pump motor 44 will be interrupted by theactuation of the switch I which will now be turned to open circuitposition. When the temperature of the room has dropped for a desiredpredetermined amount, the switch -H will serve to close again thecircuit through the resistance coil 15 and the operation of the systemwill be repeated as above described. In this manner after the operatormerely has operated the single snap switch 43, the heating equipment andthe room temperature will be entirely automatically controlled andregulated within defined limits, depending upon the sensitiveness of thethermostatic switch H. stopped when desired by turning off the power atthe switch 43.

It will be noted that when the switch F is restored to its normalposition. as illustrated, the body of mercury 25 will flow into theposition shown only when a certain time interval has elapsed after themovement of the body of mercury 20 in the switch I. This is because ofthe curved shape of the container26 of the switch F and serves tointroduce a substantial lag in the operation of the system thuspreventing the starting and stopping of the pump motor 44 at toofrequent intervals in case the thermostatic switch H is very sensitiveto slight changes in temperature.

In the operation of the system as above described, it has been assumedthat the intended ignition and combustion have taken place in the firebox A-. However, in case the snap switch 43 is thrown at a time when thepilot light C is not lighted, or if for any other reason combustion ofthe fuel does not take place, the continued operation -of the fuel pumpwould allow an excess of the fuel to accummulate within the fire box andthus create a very serious fire hazard. In the system as shown, whenlgnition does not take place, the thermostatic switch J- will remaincold and inits open circuit position and consequently when the switch Fis also turned to open circuit position, no means will remain forheating the resistance coil 15, and consequently the switches F and Iwill soon return to their initial positions thereby interrupting thecircuit to the motor 44. It will thus be evident that the pump motorwill at no time-continue in operation for more than a short intervalunless combustion takes place and the thermostatic switch J is heatedsufficiently to turn to its closed circuit position. Hence, thepossibility of accidental accumulation of large amounts of fuel in thefire-box is avoided.

We have shown in our control system the use of electric contactors, suchas the contactor 29- comprised in the thermostatic switch or safetycontrol mechanism J Of course. we do not desire that our invention be solimited except where an electric contactor is specifically called for.The terms electric contactor or mercury electric contactor as employedherein, therefore, referto a device comprising av sealed container inwhich electrodes are disposed that'are spaced from each The automaticcontrol may be cal circuit to which said electrodes are connectedthrough the medium of a movable contact member, such as the body ofmercury 32 of the cont actor 29. Other forms of electric contactors, ofcourse, may be used such as are well known in the art, but it is to beunderstood that the movable contact member,

such as the body of mercury 32, is the medium through which theelectrical circuit is'made and broken between the spaced electrodeshoused within the container.

\Vhile we have shown and described several embodiments of our invention,it is to be understood that many modifications may be made thereinwithout departing from the spirit and scope of the appended claims, andwe desire that only such limitations shall be imposed upon our inventionas are specifically pointed out in the claims and such as are requiredby the prior art.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent in the United States, is

1. A system for controlling a fuel burning device and comprising a fuelsupply means, an electric motor therefor, a control circuit for saidmotor, a room, thermostatic switch, an electrically heated relay theelectric heater circuit of which is controlled by said room thermostaticswitch and is connected in series circuittherewith, and a common sourceof power supplying both said motor circuit and the circuit comprisingsaid room thermostatic switch, said relay being provided with electricswitching mechanism. operated thereby for controlling said circuits.

2. A system for controlling the combustion of fuel comprising anelectric fuel pump motor, a source of power, an electric heatingelement, a switch through which current is initially transmitted to saidelement, means for transmitting power to said element after combustionstarts but acting upon the failure of ignition and combustion to openthe circuit through said said element, a common switch in circuit withboth said motor and said means, and mechanical means responsive to theheating of said element for opening said first named switch and forclosing said second named switch.

3.- A system for controlling the combustion of fuel comprising anelectric fuel pump motor, a source of power, an electric heatingelement, a room thermostat controlling the transmission of current tosaid element, a switch through which current is initially transmitted tosaid element, means for transmitting power to said element aftercombustion starts but acting upon the failure of'ignition and combustionto open the. circuit through said element, acommon switch in circuitwith both said motor and said means, and mechanical means responsive tothe heating of said element for opening said first named A combustionstarts,but acting upon the failure of ignition and combustion to openthe circuit through said element, a common switch in circuit with bothsaid motor and said means, and mechanical means responsive to theheating of said element for opening said first'named switch and forclosing said second named switch, said mechanical means upon becomingcool serving to restore said switches to their initial positions.

5. An electrical control system for an oil burner comprising a'temperaturecontrol thermostat, a thermostatically controlled actuator,an electric heating element for said actuator the circuit of which iscontrolled by a circuit comprising said thermostat, a combustionchamber, electrically controlled means for supplying fuel thereto, anelectric switch controlling said fuel supplying means, said electricswitch adapted to be held in closed position by said actuator whenheated, and safety control means for controlling said electric switch tomaintain the same in closed position as long as combustion obtains butpermitting said electric switch to move automatically into open positionupon failure of combustion.

6. An electrical control system for an oil burner comprising atemperature control thermostat, a thermostatically controlled actuator,an electric heating element for said actuator the circuit of which isconnected in circuit with said thermostat, a combustion chamber,electrically controlled means for supplying fuel thereto, an electricswitch controllin said fuel supplying means, said electric switch beingcontrolled by said actuator, and safety control means constituting athermo sensitive element. influenced by combustion conditions obtainingin said combustion chamber, said safety control means controlling saidelectric switch to maintain the same in closed position as long ascombustion obtains but permitting said electric switch to moveautomatically into open position upon failure of combustion.

, ated, said control mechanism comprising an electrically heatedthermostatic actuator, an electric switch controlling said fuel supplymeans and adapted to be held in closed position by said actuator whenheated, and a thermostatic device responsive to temperature conditionsobtaining in the combustion chamber for causing said switch to remainclosed when combustion obtains and permitting said switch to open uponfailure of combustion thereby precluding continuous operation of saidfuel supply means.

8. In a control system for a fuel burning device comprising a combustionchamber, and electrically controlled means for supplying a fuel mixtureinto a zone of ignition therein, the combination with a temperaturecontrol thermostat, a thermostatically controlled actuator, anelectrical heating element for said actuator the circuit of which iscontrolled by said thermostat, of an electric switch adapted to be heldin closed position by said actuator when the latter is heated, saidelectric switch controlling the operation of said fuel supplying meanswhen said thermostat is closed, and a safety control mechanisminfluenced by the combustion conditions obtaining within said combustionchamber for .causing said J electric switch to remain in closed positionas long as combustion continues but permitting said electric switch tomove to open circuit position upon initial failure of combustion orfailure of continuous combustion within said combustion chamber.

9. In a control system for a fuel burning device comprising a combustionchamber, and electrically controlled means for supplying a fuel mixtureinto a zone of ignition therein, the combination with a temperaturecontrol thermostat, a thermostatically controlled actuator, anelectrical heating element for said actuator the circuit of which iscontrolled by said thermostat, of an electric switch adapted to be heldin closed, position by said actuator when the latter is heated, saidelectric switch controlling the operation of said fuel supplying meanswhen said thermostat is closed, and a safety control mechanismcomprising a thermo sensitive element that is influenced by thetemperature conditions obtaining within said combustion chamber, saidsafety control mechanism causing said electric switch to remain inclosed position as long as combustion continues but permitting saidelectric switch to move to open circuit position upon failure ofcombustion within said combustion chamber.'

10. A fuel burning device comprising a combustion chamber, means forsupplying a fuel mixture into a zone of ignition therein, and anelectrical control mechanism for preventing the supply of the fuelmixture upon initial failure of ignition or failure of comcontrolmechanism comprising an electrical circuit having an electrically heatedthermostatic actuator for controlling the operation of said fuelsupplylng means, til-temperature control thermostat connected-in saidelec trical circuit which also comprises the electric heater circuit .ofsaid actuator, and a safety control mechanism responsive to combustionconditions. obtaining within said combustion chamber for controlling theopera tion of said fuel supplying means.

11. A fuel burning device comprising a combustion chamber, means forsupplying a fuel mixture into a zone of ignition therein, and anelectrically controlled mechanism for preventing the supply of the fuelmixture upon initial failure of ignition or failure of combustionconditionsthereafter, said control mechanism comprising an electricalcircuit having an electrically heated thermostatic actuator forcontrolling the operation of said fuel supplying means, a roomthermostat controlling said electrically heated thermostatic, actuator,an electric switch controlling said fuel supplying means and which isheld in closed circuit positionby said electrically heated thermostaticactuator when the latter is heated, and a'safety control mechanisminfluenced bycombustion conditions obtaining within said "combustionchamber for causing said electric switch to remain in closed position aslong as combustion conditions obtain within said combustion chamber butpermitting said electric switch to move to open circuit position uponfailure ofcombustion within said combustion chamber. l

12. In an electrical control system for a fuel burning device comprisinga. combustion chamber, electricallycontrolled means for supplying a fuelmixture into a zone of ignition therein, and an electric switch forcontrolling the operation of said fuel supplying means, the combinationwith an electrically heated thermostat for actuating said electricswitch to holdthe same in closed position when said thermostat isheated, of a safety control mechanism sensitive to combustion conditionspermitting said electric switch to move to open position upon initialfailure of combustion or failure of combustion to continue thereafterbut causing said electric switch toremain in closed position as long ascombustion obtains withiri said combustion chamber.

13. In a control system fora fuel burning device comprising a combustionchamber, and electrically controlled means for supplying a fuel mixtureinto a zone of ignition therein, the combination with an electric switchfor controlling the operation of said fuel supplying means, of anelectrical control mechanism for controlling the operation of saidelectric switch to prevent the supply of the fuel mixture upon aninitial failure of combustion or failure of combustion conditions afterignition, said control mechanism comprising a safety device embodying ac'asing, a mercury electric contactor housed in said casing and having acontainer, spaced electrodes fixed therein and a movable contact memberto control the circuit between the electrodes, a thermal responsivedevice for controlling the movement of said movable contact memberrelatively to said fixed electrodes to, close an electric circuitthrough said mer'cury electric cont-actor when said thermal responsivedevice is relatively hot and to open said circuit when said device isrelatively cold, said thermal responsive device being supported upon andprojecting outwardly from said casing and so disposed as to be subjectedto temperature changes occurring within said combustion chamber and saidcasing being spaced from said thermal responsive device and disposed ina relatively cool region, said mercury contactor through the medium ofsaid movable contact member controlling the operation of said firstelectric switch to break the electric circuit therethrough when saidthermal responsive device is cold by reason of initial failure ofcombustion or failure of combustion conditions after ignition withinsaid combustion chamber.

14. In a control system for a fuel burning device comprising acombustion chamber, and electrically controlled means for supplylng afuel. mixture into a zone of ignition therein, the combination with anelectric switch for controllingthe operation of said fuel supplyingmeans, of an electrical control mechanism for controlling the operationof said electric switch to prevent the sup-- tween said thermal memberand said control switch for controlling the movement of said movablecontact member to close said control switch when said thermal member isrelatively hot and to open said control switch when said thermal memberis relatively cold, independently of all other conditions of the system.

15. In a control system for a'fuel burning device comprising acombustion chamber, andelectrically controlled means forsupplying a fuelmixture into a zone of ignition therein, the combination with a controloncuit forsaid fuel supplying means comprising a room thermostatinitiating operation of said control circuit, of an electrical safetycontrol mechanism for preventin the supply of fuel mixture upon aninitial failure ofignition or failure of combustion. conditionsthereafter, saidsafety control mechanism comprising an electric switchdisposed in a relatively cool region and including rela- Cal tivelymovable contact members, a thermal responsive member so disposed as tobe subjected to combustion conditions obtaining in said combustionchamber, and a connection between said thermal responsive member andsaid electric switch for effecting relative movement between saidcontact members to close said switch when said thermal responsive memberis relatively hot and to open said switch when said thermal responsivemember is relatively cold, independently of all other conditions of thesystem.

16. A fuel burning device comprising a combustion chamber, electricallycontrolled means for supplying a fuel mixture thereto, and a controlcircuit for said fuel supplying means comprising a room thermostat whichinitiates operation of said control system, and an electrical safetycontrol mechanism for preventing the sup ly of the fuel mixture uponinitial failure of ignition, said safety control mechanism comprising anelectric switch including a container, spaced electrodes fixed therein,and a movable contact member, a member sensitive to combustionconditions that obtain in said combustion chamber for controlling themovement of said movable contact member, and a connection between saidsensitive member and said movable contact member for moving said movablecontact member relatively to said spaced electrodes to close saidelectric switch when said sensitive member is relatively hot and to opensaid electric switch when said sensitive member is relatively cold.

17. A fuel burning device comprising a combustion chamber, electricallycontrolled means for supplying a fuel mixture therein, and an electricalcontrol circuit for said fuel pro]ecting means, said control circuitcomprising a room thermostat for initiating operation of said controlcircuit, and an electrical safety control mechanism for preventing thesupply of the fuel mixture upon an initial failure of ignition or afailure of combustion conditions. after ignition, said safety controlmechanism comprising spaced contacts, a movable contact member adaptedto control the electrical circuit through said spaced contacts, athermal element sensitive to combustion conditions obtaining in saidcombustion chamber for actuating said movable contact member, and aconnection between said thermal member and said mo"- able contact memberwhereby the electrical circuit between said spaced contacts and saidmovable contact member is completed when said thermal member isrelatively hot and is interrupted when said thermal member is relativelycold. T

18. A fuel burning device comprising a combustion chamber, electricallycontrolled means for supplying a fuel mixture into a zone of ignitiontherein, and an electrical circuit controlling the operation of saidfuel tric heating cuit of whlch is connected in clrcuit wlth said Isupplying means, said electrical control circuit comprising a roomthermostat which initiates operation of said control circuit, and anelectrical safety control mechanism for-preventing the supply of thefuel mixture upon an initial'failure of combustion ing said movablecontact member, said contact members including said movable contactmember being so arranged as to complete the electrical circuittherebetween when said sensitive member is relatively hot and to interrupt the electrical circuit therebetween when said sensitive memberis relatively cold. 19. A system for controlling a fuel burn-' ingdevice, comprising fuel supply means, an electric motor therefor, acircuit for said motor, a room thermostatic switch, an electricallyheated relay the electric heater circuit of which is connected incircuit with said room thermostatic switch, and switching means embodiedin said relay and automatically actuable solely through said relay forcontrolling said motor circuit.

20. In a fuel burning system, the combination with a combustionchamber,of means for supplying fuel thereto, an electric motor for saidfuel supplying means, motor, a room thermostatic switch, an electricallyheated relay the electric heater circuit of which is connected incircuit with said room thermostatic switch, switching means embodied insaid relay and automatically actuable solely through said relay, forcontrolling said motor circuit, and safety-control means responsive tocombustion conditions obtaining in said combustion chamber forcontrolling the-operation of said relay.

21. In a fuel burning system, the combination with a combustion chamber,of electrically controlled'means for supplying fuel thereto, atemperature control thermostat, a thermostatically controlled actuator,an elecelement for said actuator the cirthermostat, an electric'switchfor controlling said fuel supplying means, said electric switch beingcontrolled by said actuator alone to maintain energization 'of said fuelsupplying means temporarily, and safety control means comprising athermo sensitive element influenced by combustion conditions obtainingin said combustion chamber, said safety control means supplementing thecontrol of said electric switch to maintain energization of said fuelsupplying means as a circuit for said long as combustion obtains in saidcombustion chamber.

22. In a fuel burning system, the combination with a combustion chamber,of elecbustion chamber, and a switch operable by said element, saidlast-mentioned switch being connected in parallel circuit relation tosaid first-mentioned switch to maintain energization of said fuelsupplying means independently of said first-mentioned switch as long ascombustion obtains in said combustion chamber. 23. In a fuel burningsystem, the combination with fuel supply means and an. electric motortherefor, of a control system for said motor, said control systemcomprising an element capable of being'electrically energized to efi'ectoperation of said motor, a room thermostatic switch, acontrol switcharranged to cooperate with saidroom thermostatic switch to effectinitial energization of said element, and a su plemental switch arrangedto maintain su sequent energization of said element subject to theoperation of said room thermostatic switch, said control switch beingrelatively slow in its operation to prevent immediate reenergization ofsaid element after deenergization thereof in response to the operationof said room thermostatic switch.

24;. In a fuel burning system, in combination, a combustion'chamber,ignition means therein, fuel supply means, an electric motor therefor,and a control system for said motor, said control system comprising anelement capable of beingelectrically energized to effect operation ofsaid motor, a room thermostatic switch for normally controlling theenergization of said element, and a safety control mechanism forrendering said element ineffective to maintain energization of saidmotor upon failure of ignition in said combustion chamber or uponfailure of combustion after ignition and for preventing reenergizationof said element immediately after the termination of a period ofcombustion, said safety control mechanism comprising a member sensitiveto combustion conditions obtaining in said combustion chamber, a switch0 erable by said member, and a switch operable in response to theenergization of said electricall .energizable element, saidlast-mentions two switches being respectively disposedin twoparallel-connected circuit branches.

25. In a fuel burning system, in combination, a combustion chamber,ignition means therein, fuel supply means, an electric motor therefor,an element capable of being electrically energized to effectenergization of said motor, and means for controlling the energizationof said element to effect energization of said motor under predeterminedconditions but. to interrupt energization of said motor upon failure ofi nition in said combustion chamber or upon ailure of combustion afterignition and to prevent reenergization of said motor immediately afterthe termination of a period of combustion, said controlling meanscomprising a plurality of switches disposed in circuit controllingrelation to said element, one of which switches is so constructed as torequire a substantial interval of time to move from open to closedposition, and a member sensitive to combustion conditions obtaining insaid combustion chamber for controlling the operation of one of saidswitches.

' In witness whereof, we have hereunto subscribed our names.

LOUIS A. M. PHELAN. CLIFFORD HOTCHKISS.

CERTIFICATE OF CORRECTION.

Patent No. 1,764,344. Granted June 17, 1930, to

LOUIS A. M. PHELAN ET AL.

It is hereby certified that error appears in the above numbered patentrequiring correctionas follows: In the heading to the printedspecification, assignment, name'of assignee for "Indiana Ti'me-O-StatControls Company" read Time-O-Stat Controls Company; page 5, line 110,claim 2, strike out the word "said" second'occurrenee; page 8, line 25,claim 16, after the word "member" insert "to control the electriccircuit through said spaced electrodes"; and that the said LettersPatent should be read with these corrections therein that the same mayconform to the record of the case in the Patent Office.

Signed and sealed this 9th day of September, A. D. 1930.

v M. J. Moore, (Seal) v Acting Commissioner of Patents.

